The Linux kernel can be built either using the module's Linux system or on the Linux Host Machine, using a cross-SDK. In either case, the development tools need to be made available, as discussed in the Yocto Build section, chapters 2 and 3.
The build process itself consists of obtaining the proper source code and invoking make for the correct module.
1. Fetch the kernel sources and enter the directory
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$ git clone <https://git.congatec.com/arm-nxp/imx8-family/kernel-imx8-family.git>
$ cd kernel-imx8-family |
2. Switch to the appropriate branch
In this step a version that will be built needs to be selected in the downloaded Git repository. Selected can be either the latest version of a congatec branch (2a) or a particular version, usually tight to a software release (2b). The available congatec branches, together with identification of the base NXP version and list of congatec releases on each branch can be found in the table below.
Kernel Version | NXP Release Suffix | congatec Kernel Branch | congatec Release Tags | Module Revision |
|---|---|---|---|---|
4.14.98-2.0.0 | 2.0.0_ga | cgtimx8mm__imx_4.14.98_2.0.0_ga | rel_cgtsx8m_20-06-16-0 | A |
5.4.47-2.2.0 | 2.2.0 | cgtimx8mm__imx_5.4.47_2.2.0 | rel_cgtsx8m_21-03-16-0 | A |
5.15.32-2.0.0 | 2.0.0 | cgtsx8m__lf-5.15.32-2.0.0__cgtsx8m-A | N/A | A |
5.15.32-2.0.0 | 2.0.0 | cgtsx8m__lf-5.15.32-2.0.0 | rel_cgtsx8m_23-02-22-0 | B |
2a. Selecting the latest version from a branch
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$ git checkout <Kernel Branch> |
2a. Selecting a particular version
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$ git checkout <Release Tag> |
3. Build kernel
The build process consists of two steps - selecting the desired make target and the build itself.
Available make targets can be found in the table below; the selection is made based on the module the kernel is intended for.
Module | Kernel Make Target |
|---|---|
conga-SMX8-Mini | sx8m_defconfig |
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$ make <Kernel Make Target>
$ make |
4. Deploy kernel modules to the destination root filesystem
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$ make INSTALL_MOD_PATH=/path/to/the/filesystem/mountpoint modules_install |
The following files are created during the build process; the kernel image file has the same name for every module while the name of the default device tree file is module specific.
Role | Subdirectory | File name | Module |
|---|---|---|---|
The kernel image | arch/arm64/boot | Image | All |
The default DTB | arch/arm64/boot/dts/congatec | imx8mm-cgtsx8m.dtb | conga-SMX8-Mini |
The default DTB file instructs the kernel to take over information about resolution from the bootloader. A specific resolution can be defined directly in the kernel DTB - in the DTB directory can be found several resolution and video output specific DTBs (they are named accordingly). Note that the resolution defined in bootloader is in this case used only for video output in the bootloader itself. Together with every compiled device tree file (.dtb) is present its source file (.dts); it can be used as a base for user modifications.